In general, building code guidelines for high rise condominium or apartment buildings, for example, require that domestic hot water enter the individual units or suites at a specific temperature in order to avoid potential scalding. For example, building codes may require that the water enter the units or suites at a temperature less than or equal to 125° Fahrenheit. However, to avoid the accumulation of harmful bacteria within the domestic hot water supply when the water is stagnant within a storage tank, building codes typically require that water be kept at a minimum temperature of at least 140° Fahrenheit. Accordingly, the domestic hot water supply requires tempering between the storage tank where the hot water is stored and upon entering the individual units or suites in order to bring the hot water to the required, usable temperature in accordance with known guidelines.
Domestic hot water distribution systems are known wherein the domestic hot water is tempered mechanically using an anti-scalding mixing valve. Typically, the anti-scalding mixing valve is an electronic mixing valve having two inlets, one for domestic hot water and one for domestic cold water, and one outlet for the tempered water. The mixing valve can be set, by means of a control system, based on the inlet temperatures of both the domestic hot water and the domestic cold water to ensure appropriate mixing of the domestic hot water supply and the domestic cold water supply to bring the temperature of the domestic hot water that is delivered to the individual units/suites, etc. to the required temperature, e.g., 120-125° Fahrenheit.
Typical anti-scalding mixing valves, however, have a minimum flow requirement in order for accurate mixing to occur. Therefore, the typical anti-scalding mixing valve requires that a certain flow rate be maintained through the system in order to ensure appropriate functioning of the mixing valve and the overall water tempering system. However, during periods of low usage or low demand on the water supply, for example, during the overnight period, the main circulator pumps, which pump the hot and cold water through the overall water distribution system, are turned off or are not in use for energy saving purposes and a recirculation pump is often used to run hot water through the building. Very often, the pump rate of the recirculation pump is lower than the minimum flow rate required for the proper functioning of the anti-scalding mixing valve to ensure accurate mixing. Accordingly, during periods of low usage there is a risk that accurate mixing and accurate tempering of the domestic hot water will not occur, raising the risk associated with possible scalding. Furthermore, reduced flow through typical anti-scalding mixing valves tends to cause calcium build-up within the valve causing the valve to cease or fail, which cessation or failure further increases the risk of scalding due to the tendency of the anti-scalding mixing valves to malfunction or fail. Therefore, it has been found that the tendency for anti-scalding mixing valves to malfunction or fail due to improper mixing resulting from reduced flow rates through the valves and/or calcium build-up, increases the overall service and maintenance requirements of typical or standard watering tempering systems that are often found in high-rise buildings.
Accordingly, there is a need for improved water tempering systems or improved temperature control for water distribution systems that not only improves performance and reliability but that also is more cost effective.